It's Raining Inside my Garage

I'm starting to feel lame for the number of posts involving my garage, but I need to vent. I was frustrated this morning to find that, despite being stored in the garage, my car got not only wet, but also muddy from last night's rain. The structure is situated such that roof is slightly lower than the level of the ground on two sides and in a heavy rain the mud can flow right through the gaps between the corrugated roof and and walls. Thank you Tropical Storm Sinlaku (Turned Typhoon Sinlaku) for all your rain and gray skies.